The present invention relates in general to roller conveyor systems, and more particularly to load transporting and storing conveyor systems formed of non-powered conveyor rollers and a load advancing car, or monitor car, which engages and advances loads along the non-powered conveyor rollers from a feed end to an unloading end and senses the positions of loads already advanced to the unloading end to automatically position later transported loads in predetermined closely spaced relation thereto.
Heretofore, powered conveyor roller systems have been in wide use for transporting loads along a conveyance path from an infeed end or loading station to a discharge or unloading end, wherein the loads to be transported rest on the powered conveyor rollers and are driven by frictional contact with the roller surfaces to advance them to the unloading end of the conveyor path. While these powered conveyor roller load transporting systems have been used in many different industries and arts, the ensuing description will be directed primarily to the use of conveyor systems in advancing loads such as stacks of corrugated paper board or cardboard from a loading or feed station to a discharge or unloading station. For example, the loading or feed station may be located adjacent a corrugating machine or adjacent a transfer car movable along a supply lane, and the discharge or unloading end may be provided with a brake belt or similar mechanism for stopping the load at a position where an operator can unload the cardboard blanks into further processing machinery or onto a transfer car adjacent a line of such machinery. Such powered conveyor roller systems have been used frequently to transport stacks of corrugated paper board from a corrugating machine or corrugator to a brake belt at an unloading position, where an operator manually transfers the cardboard blanks, in stacked subdivisions of sizes convenient for the operator to handle, to a printer-slotter machine, which prints, scores and slots the cardboard blanks for further processing at a mechanical folder or stacker, or the operator may manually load the cardboard to more modern folder-gluer machines which print, slot, fold, glue, count and stack the blanks. The powered roller conveyor systems conventionally used in that application involve a long line of conveyor rollers positioned for rotation about parallel axes disposed transverse to the direction of the conveyor path and journalled in suitable bearing structures so that their axes of rotation lie in a common horizontal plane, frequently spaced about 1 foot above the floor line. The lower surfaces of these driven conveyor rollers are engaged by the upper flight of an endless drive belt having one end trained about an idler drum and the other end about a driven drum driven by a suitable chain and sprocket drive mechanism from a drive motor. The belt is usually trained back and forth about a plurality of tensioning drums or pulleys to control the belt tension. Customarily, a plurality of serially arranged zone control tension roll sections underlie the drive belt and are each formed of a plurality of rolls journalled in a vertically movable frame of some chosen length. These zone control sections are located in series along the whole length of the conveyor roll path and bear upwardly against the upper flight of the drive belt to ensure driving friction between the driving belt and the conveyor rollers when adjusted to their raised positions so that the conveyor rollers above them are driven to advance the load from the feed end to the discharge end. Air bags or other vertically adjustable mechanisms are provided to support the opposite ends of each zone control tension roll section and are controlled by signals or mechanisms slaved to a photocell monitoring system to lower selected zone control roll frames and thereby terminate the driving of the conveyor rollers associated with that frame when it is desired to terminate advancing of the load on the rollers above that frame. Typically, a photocell monitoring system is provided a short distance back of the discharge end of the conveyor system, for example, about three feet upstream from the discharge end, to sense the arrival of a stack of blanks or other load at that location and activate the control mechanism for the last downstream zone control roll section to withdraw the driving force from the conveyor rollers supporting the stack which has arrived at the discharge end. Typically, other photocell monitoring units are provided spaced at intervals of about fifteen or twenty feet upstream from the monitoring station at the discharge end to detect arrival of other stacks of blanks or load at the spaced upstream monitoring positions to withdraw the drive from the belt to the conveyor roller at the upstream monitoring stations and stop the subsequent loads at those stations by lowering the associated zone control roll frame section.
A number of disadvantages have been recognized in connection with such powered live roller accumulating conveyor systems. For example, because of the sectioned tension roller type of construction employed and the customary disposition of monitoring photocells, accumulation of load stacks on the conveyor line is severely limited as, for example, when one stack has been advanced to the unloading or discharge end of the conveyor and is being stored at the unloading end, the leading edge of the next load stack to be advanced along the conveyor and stored thereon cannot be nearer to the leading edge of the unloading end stack than the distance between the first and second monitoring photocells along the path, which is usually about fifteen or twenty feet. Even with a closer spacing of monitoring photocells, with a consequent significant increase in cost of installation, the percent storage which can be achieved with such a powered live roller conveyor line is limited to the sectional tension roll construction, since subsequent load stacks to be stored can be brought no closer to the previously advanced stack than the adjoining tension roll section, and such sections are customarily at least 5 feet long.
Also, if a customer desires to lengthen such a powered live roller accumulating conveyor system already installed on his premises, and desires to continue the capacity to accumulate plural load stacks along the conveyor at the respective photocell monitoring stations, he would have to increase the drive motor power requirements for the lengthened line, thus greatly increasing the cost beyond the mere installation of additional conveyor rollers and tension sections.
An object of the present invention, therefore, is the provision of a novel non-powered roller conveyor for transmitting loads between a feed end and an unloading end, wherein a load monitoring transporting car is provided driven by a reversible drive system to move between the two ends for advancing loads along the conveyor line and for sensing where adjacent load stacks at the unloading end are located and to advance successive load stacks to storage positions so closely adjacent to the already advancing load as to obtain close to one hundred percent storage capacity on the conveyor.
Another object of the present invention is the provision of a non-powered conveyor system of the type described in the immediately preceding paragraph, wherein the monitoring car is provided with a movable friction pad and controlled by a mechanism which senses the presence of a load in certain zones relative to the pad to advance the pad into contact with the underside of the load and pull the load along the conveyor line to a position closely adjacent to the last previously advanced stack and thereupon release the load for storage thereat.
Yet another object of the present invention is the provision of a non-powered roller conveyor system of the type having a load sensing monitor car for advancing the load along the conveyor system to storage position, which provides maximum storage accumulation of loads along the roller conveyor line with very small spacing between load sections, which automatically sense the position of the previously advanced load already in storage regardless of the horizontal dimensions of the load stack to deposit the next advanced load stack closely adjacent to the previously advanced stack, and wherein conveyor lines can be readily lengthened without increasing driver power since the monitor car advances only one stack at a time.
Another object of the present invention is the provision of a non-powered roller conveyor system of the type described in any of the three immediately preceding paragraphs, wherein installation costs for relatively long accumulating roller conveyor lines beyond a certain short line size are significantly more economical than conventional powered live roller conveyor systems.
Other objects, advantages and capabilities in the present invention will become apparent in the following detailed description, taken in conjunction with the accompanying drawings illustrating the preferred embodiment of the invention.